In "I Don't Know How She Does It," which opens this month, Sarah Jessica Parker's character bolts frantically from demanding job to loving husband to her two kids — the quintessential "have it all" woman who ends up having everything halfway.

Late to meetings, falling asleep before sex and bursting into tears when she misses her son's first haircut, Parker's heroine confesses: "I love my work, although sometimes I wish I didn't love it so much."

Such is the conundrum in the quest for work-life balance, a kind of holy grail for modern fulfillment. We aspire to love our jobs and accomplish great things, yet in seeking balance we rob some of that energy to direct it elsewhere.

As Carrie Bradshaw might have put it in Parker's former life: Does passion suffer when you impose moderation?

Akhila Kolisetty thinks it might. Kolisetty, 22, a recent college graduate working in Washington, D.C., is choosing to forsake balance to focus on her job at a civil rights law firm and her volunteer work at a nonprofit that provides legal aid to Afghan women. She estimates she spends about 70 hours a week on that work, plus more weekend hours writing grants for the nonprofit, leaving a couple of nights free to spend time with friends.

"If I want to be able to make the most impact, I have to spend this amount of time," Kolisetty said, adding this is the time to do it because she has few family obligations.

It is a controversial opinion, as Kolisetty discovered when she wrote about her anti-balance philosophy in a blog post earlier this year and was slammed with angry comments testifying to the physical, emotional and mental toll that a single-minded pursuit of work had on people's lives.

With a third of U.S. employees overworked and reporting more mistakes and poorer health as a result, experts and studies say there's value in moderation — and rather than dampen passion, balance helps fortify it.

First, define 'balance'

What a healthy balance entails is different for everyone — and it might not even be the right word.

Rather than seek "balance," which connotes a 50-50 split or an either/or bargain, Judy Martin views the struggle as a work-life "merge" to account for our culture of 24/7 accessibility.

Many people fear they'll lose their competitive edge if they put down their BlackBerry for a minute, but it's a recipe for burnout, said Martin, who works as a TV news anchor in Long Island and runs worklifenation.com, where she explores workplace issues.

The key to managing the merge, she said, is prioritizing the things that are most important to you and communicating boundaries to employers, spouses and anyone else who demands your time.

"It's about going into the boss's office and having a solution," Martin said. That might mean asking to come in early so you can leave early for school pickup, or designating dinnertime off-limits to work calls but vowing to check in right after.

Martin's interest in workplace wellness began when the Twin Towers tumbled a decade ago. Reporting on the attacks for a radio program, Martin found a way to manage her stress and grief by volunteering each night to sit with the kids of survivors who trekked to ground zero searching for loved ones.

For Martin, balance meant making time to volunteer and meditate so she could refuel. But it's up to each individual to figure out an energy source.

For Kathy Caprino of Connecticut, balance meant seeking work that mattered and making room for hobbies she had long neglected. After 18 years chasing money and ego up the corporate ladder, with her leftover time spent with her two kids, Caprino felt depressed, angry and chronically ill.

Her turning point also came with 9/11, when she was laid off in the ensuing economic crash. She was so one-dimensional at the time, she said, that she continued to put on a suit every morning and just drive around.

Eventually, after trying on a new hat as a therapist, Caprino founded Ellia Communications, a career coaching business that meshed her knowledge of the corporate world with her passion for helping people. She said she works constantly, more than she ever did before, but she can carve out time for other interests, such as tennis and singing, as well as her family.